


Poseidon's Prisoner

by esteoflorien



Category: Harry Potter - J. K. Rowling
Genre: Gen, Muggle London, Muggle/Wizard Relations, Squibs
Language: English
Status: Completed
Published: 2015-04-26
Updated: 2015-04-26
Packaged: 2018-03-25 19:06:02
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,452
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/3821470
Author URL: https://archiveofourown.org/users/esteoflorien/pseuds/esteoflorien
Summary: <blockquote class="userstuff">
              <p>Young Cassiopeia Black sets off in search of her brother - and receives assistance from an unlikely person, making her reconsider the way she previously viewed her world.</p>
            </blockquote>





	Poseidon's Prisoner

**Author's Note:**

  * For [Alley_Skywalker](https://archiveofourown.org/users/Alley_Skywalker/gifts).



> Thanks for the wonderful prompt, Alley_Skywalker! I hope you enjoy the story as much as I enjoyed writing it!

Cassiopeia Black wasn’t sure what she was expected when she slipped outside the confines of the Leaky Cauldron and into muggle London, but it certainly wasn’t this. The streets were bustling and filled with moving vehicles, most small, but others larger, interspersed with the very occasional horse and carriage. The vehicles spat out smoky exhaust that spiraled round and made her throat constrict and her eyes water.

She steeled herself to cross the street, but just as she’d managed to summon her courage, she felt a gloved hand pull her firmly back onto the sidewalk. “You’ll get yourself killed!” a woman practically shouted. “Where are you off to?”

Cassiopeia looked up and found herself face-to-face with her first muggle: an older woman with dark hair pinned back like her Grandmother Black and held in place with a small blue hat. Her clothes were similarly fine: a long, sweeping grey coat with embroidered lapels fastened over a blue dress, with a matching scarf at her neck. Her gloves were soft leather, and muggle or not, Cassiopeia was perfectly able to recognize wealth when she saw it. She stood straighter and wished she’d worn a better dress. As it was she felt terribly out of place, terribly old-fashioned; she’d seen many girls trot past her, and not a single one was wearing a taffeta bow like hers in their hair.

“I’m looking for my brother, ma’am,” she said. “He’s away at school.”

A look of confusion crossed the woman’s face. “Your brother is away at school in London?” Her voice was clear but she spoke with an unfamiliar accent, one that seemed to around her words like silk.

“Yes,” Cassiopeia mumbled, and fished the scrap of paper onto which she’d scrawled Marius’s address out of her school satchel. She handed it to the woman. “I’ve lost my way.”

The woman shook her head. “And where is it _you_ go to school, dear?”

Cassiopeia sighed. She hadn’t prepared herself for lying. “In Scotland, ma’am. I’m at school in Scotland you see, and my brother is here and I –”

The woman sighed. “I presume your parents are entirely unaware of this excursion,” she asserted.

“Mother said I could have a walk about the city,” Cassiopeia said, surprising herself with the evenness of her voice. “And I _am_ having a walk. I’m just walking to one place in particular.”

“You’ll need a car to get there,” the woman said. Like magic – _magic_ , Cassiopeia thought to herself, and laughed, as if there was magic in muggle London – a sleek black car rumbled towards them. A gentleman whom she knew to be a servant but whose dress was finer than her father’s jumped out and opened the door. The woman gestured towards the car, and against her better judgment, Cassiopeia slid in.

“St. Paul’s School, Spencer,” the woman announced once the man had once again taken his place in the car.   

Spencer, Cassiopeia imagined, eased the car into traffic, but to her, the unaccustomed motion felt rather like an earthquake, like it had when their Care of Magical Creatures professor had gone and brought a miniature dragon to the Quidditch field. To her embarrassment, she pitched hard to the side, practically falling into the woman’s lap.

“Careful,” she said, her voice laced with concern. “Have you never been in a car before, my dear?”

Cassiopeia sighed. “My parents don’t believe in cars,” she said simply. Grandfather Black insisted that the best lies were the ones with an element of truth, and though she imagined lying would never come easily to her, she was a daughter of the House of Black and she knew when prevarication had the better part of valor.

“Ah, I see,” the woman said. “What did you say your name was, dear?”

“I didn’t,” Cassiopeia replied, smartly. “But neither did you.”

The woman smiled. “Neither did I. I am Mrs. Astor. And you are?”

Her name meant nothing to this muggle woman, Cassiopeia reasoned. Surely there was no harm in telling her, and if she gave a false name, she’d have to remember it. “I am Cassiopeia Black,” she said, as she would have had this woman been a Malfoy, or or a Yaxley, or even a Potter. “Of the Noble House of Black,” she added, when the woman’s expression remained unchanged.

“I am unaware of a noble House of Black,” she murmured. “Where is your family seat?”

“In the country,” Cassiopeia replied, and the woman laughed.

“Very well, my dear,” she said, after a long moment. “You may keep your secrets, although if I did know your mother, I can assure you I would not have informed her of your journey, assuming you promise not to undertake one again.”

“Mother wouldn’t be very pleased with me for going to see my brother,” she finally said. “But I don’t think it’s right to not visit him. Are your children away at school?”

“Yes,” the woman replied. “My sons are at Eton, and my daughter boards as well.”

“But you visit them? And you send them letters?”

The woman looked rather surprised. “Well yes, of course.”

“My parents don’t believe in that,” she declared. “So I think Marius deserves a visit, don’t you?”

The woman nodded. “I rather suppose he does.”

~

St. Paul’s School was across the river, bordered by what seemed like acres of green space. As the car made its way up the drive, Cassiopeia could see the boys come into view, all dressed in the same uniform, much as they were at Hogwarts, though from what she could see, the delineation between their houses was far less distinct.

They stopped before the main building, and Spencer darted around to open Mrs. Astor’s door. “Come, Miss Black,” she said. “Let’s find Master Black.”

Cassiopeia found herself relieved to have someone accompanying her to the office and the residence hall. Everything seemed to come easily to Mrs. Astor - _Master Black_ , she said, and it was as if everyone around them leapt into motion - and it occurred to her that if Mrs. Astor hadn’t been there, she wouldn’t have had the faintest idea how to proceed.

As it was afternoon recess, which Mrs. Astor explained was the time between the last day’s class and the evening meal, they were directed to Marius’s dormitory, which, Cassiopeia was sorry to see, was halfway across the campus and up several flights of stairs, in a white-brick building.

“At my school, the dormitories and classrooms are all in the same building,” she said, thoughtlessly, as they made their way across the campus.

“You must attend quite the school, Miss Black,” she replied, with equanimity. Cassiopeia rather thought she didn’t believe a word of it.

“It’s in a castle,” she said. “In the Scottish highlands. Today is my last day home because prefects return two days earlier than other students. My train leaves tomorrow afternoon.”

“I’m not surprised you’re a prefect,” Mrs. Astor said, with palpable amusement.

“Marius doesn’t know,” she confided. “He doesn’t come home at the holidays.”

“I can see that,” she replied, and said no more.

Cassiopeia knocked gently on Marius’s door. It was nondescript, like everything else in the building; painted white with glass knobs, it was nothing like the door to the girls’ Ravenclaw dormitory, much less the door to Ravenclaw Tower itself, with its disgruntled knocker.

She held her breath when she heard the telltale scraping of a chair and footsteps treading gently on the planks. The door opened and her brother appeared, and Cassiopeia hardly knew what to say.

“Cassiopeia,” Marius breathed, gone pale as if he’d seen a ghost.

Mrs. Astor smiled. “I shall wait for you in the hallway, Miss Black,” she said, and slipped out.

It was clearly Marius, of course, but he was at once her brother and not; he looked different - looked muggle. His hair was cut in the manner that all the boys’ hair seemed to be; he wore his clothes differently now that he was wearing trousers and fitted shirts instead of robes.

“I didn’t expect to see you, Cassiopeia,” he murmured. “How on earth did you get here?”

“I found the address in father’s study,” she said simply. “And I’m going back to Hog-to school tomorrow, and this was my last chance before December.”

“I can’t believe my goody-two-shoes sister broke the rules so very colossally!” Marius sounded impressed. “I can’t believe you risked father finding out.”

“I’m not worried about father,” Cassiopeia replied.

“I suppose not,” Marius said. He sounded older than his years. “Most talented witch and all that.”

“It has its privileges,” she said quietly. “I’m a prefect this year.”

“That’s wonderful,” Marius said. “Everyone must be proud.”

“I suppose.” Their conversation sounded stilted; she hated it.

“Does everyone miss me then?” Marius offered, and she knew it was meant to be humorous, but there was little humor in accuracy.

“I miss you,” Cassiopeia said, for it was the truth. “Do you miss us?”

Marius smiled sadly, his dark hair falling just barely into his face as he ducked his head. “I miss you,” he said, after a moment, and Cassiopeia supposed this was how things would be from now on. “Cassiopeia,” he began, sounding not for the first time like the elder of their pair, “you know I won’t be coming back home. It’s as much my decision as it is theirs.”

“I’m aware,” she said, after a long moment. “But your not coming home doesn’t mean I can’t come here. I shall simply develop an appreciation for the capital.”

“You’re certainly making the right friends,” Marius said, shaking his head. “I don’t know how you do it.”

“We ran into each other on the sidewalk,” Cassiopeia said, ignoring the fact that Ravenclaw or not, she had been too stupid to look before crossing the street. “And then she offered to help me find you.”

“I’m glad you came,” Marius said, after a moment. “It’s been so long, I thought perhaps you might not have ever come.”

“I simply had to find you,” she said. “It just took me longer than I thought. I shall do my best to come visit during the year, but as a prefect - “

“If you come,” Marius said, “send a letter and take the train from Hogsmeade to Kings Cross, and I shall meet you at the train station. Next time you might not be so lucky as to cross paths with the Viscountess Astor.”

“Very well,” Cassiopeia said. “But we won’t leave it so long.”

“Not so long,” Marius agreed, and out of nowhere, the bells began to toll. “Evening meal,” he supplied.

“Oh,” Cassiopeia said. It seemed cruel to have to leave now, after years of not speaking.

“You’ll come again,” Marius said. “Come before Christmas.”

“I shall,” she said. “I promise.” She meant it more than she had ever meant anything else, and hugged him tightly.

“You’re different than everyone else, you know,” he said. “Different from non-magical folk. I notice the magic in you now. I never did before.”

She smiled, squeezed his hand, and stepped out to return to Mrs. Astor.

~

Mrs. Astor said little on the trip back to the avenue where they had first met. To Cassiopeia’s surprise, she hadn’t even argued when she’d asked her to simply drive her back there, rather than to the train station, which was admittedly a far more logical choice. Instead, she looked at Cassiopeia appraisingly, as if she were trying to puzzle her out, for she knew that Mrs. Astor had believed only a small amount of what she’d said. After all, she would hardly have believed it herself if she didn’t _know_ that she went to school in a castle.

“You know,” she said, once the car had pulled to the sidewalk, “I’ve always liked to think that Queen Cassiopeia managed to escape Poseidon’s punishment.”

“You know the story!”

Mrs. Astor nodded, as if to say _of course I do_. “I think that she’s got the better of him, and that when he’s not looking, she does as she pleases. But when he does look, there she is, dutifully chained to her chair, until her next chance to go dancing.”

“Dancing!”

“Yes,” Mrs. Astor said, her tone quite seriously, such that Cassiopeia regretted her own levity. “Remember that. Queen Cassiopeia might be chained to the chair, but I think she finds her own way.”

Cassiopeia nodded and smiled, at this muggle woman who had proven sharply intelligent and surprisingly kind, nothing like what she had been led to believe muggle women actually were. This, her kindness and her concern and her storytelling, was a kind of magic she knew to be lost on her father and wizards like him. Perhaps it meant that Marius had his own magic, too.

She watched Mrs. Astor settle back against the seat and wave as the car drove off, and only when it was fully out of sight did she begin to turn back towards the Leaky Cauldron, back to a world that suddenly seemed different, now that the sights and sounds and smells of London ricocheted about her memory.

~

“Muggle London,” her father said, his disappointment practically tangible.

“I wanted to see where Marius – “

“I wasn’t aware that we had acquaintances in Muggle London,” her father said, sharply.

“I – “ Cassiopeia looked to her mother, who had turned her attention towards the fire. It glinted off her black hair, making it glow red. It was a familiar sight – how many times and she and her siblings been corralled into the parlor by their governess, dressed and groomed specially for teatime, and been greeted by her mother’s profile like this, half-shadow, half-incandescent outline? – but for the very first time, she saw that the fire burned with cold flame. She lifted her chin and met her father’s gaze. “I wanted to see what there was to see in muggle London. There was nothing, so I went back to Diagon Alley. It was a fool’s errand indeed.”

“I should say so,” her father said, turning his attention back to his newspaper.

Cassiopeia turned on heel and walked out, keeping her steps measured and light. “Filthy muggles,” her father barked, perhaps at her, perhaps at her mother, and then the parlor door mercifully closed.

She nicked a candle from the pantry on her way upstairs to her room. She had always had a talent with light, Cassiopeia thought, remembering the moving pictures she would make from candles, coaxing the flame to take different shapes, relishing in her little brother’s approval. They were the odd pair, close enough to practically be twins, distant enough from the others to be an entity unto themselves. It was incomprehensible that someone could simply cease to exist in the way that Marius seemed to have been erased from her father’s memory.

She thought about her brother, shut up in his boarder’s attic room, draughty and cold compared to the blazing fire in the parlor, and yet, so very much warmer than her own bedroom, with its heavy curtains and paneled bed. As happy as he was with his books and his figures, she couldn’t shake the feeling that he was lonely. The woman’s pitying gaze when she’d glanced inside his room had only reinforced it.

She propped the candle on her desk, lit it with a wave of her hand, and began to concentrate. Charms came naturally to her; magic came naturally to her. It was so thoroughly intertwined with her being that she couldn’t imagine what it was like to be Marius, to know that magic existed and yet not know how it _felt_. For she felt it: felt it winding its way through the walls of their house, felt it protecting Hogwarts, felt it flowing from her very center through her fingertips and into her wand. So many of her schoolmates had complained, on more than one occasion, that their classwork would be far easier if they could just see what it was their magic was meant to be doing. Cassiopeia had never understood it, for she could feel it, and she knew with certainty that oftentimes what one could feel was far more meaningful than what one could see. She knew, for example, that her father paid Marius’s school fees because she had seen him go to Gringotts - and yet, it was an empty gesture.

_Talented_ , the sorting hat had whispered when it’d fallen over her forehead and the world had gone dark. _Oh my, talented. You’ll be wasted anywhere but -_

“Ravenclaw,” she whispered aloud. Shame of a different sort, she supposed, though her father would never admit it - not when his Ravenclaw daughter was the most talented witch the Black family had produced in decades, and everyone - _everyone_ , especially Grandfather Black - knew it.

Tonight she felt her magic resonating with all that she had experienced that day - with the vibrancy of the city and its indefatigable hum, with the generosity of a muggle woman who her father thought below her notice, with the sight of her brother, happy, bent over his books - and she let the emotion bleed into her magic, so that she thought, if she closed her eyes, that she could see it, just for a moment, winding its way round the candle flame. She cast a succession of spells, first to make the flame dance, then to make it remember its steps, then to put it in stasis, before finally blowing it out. The final spell was the trigger spell, the one to set it dancing whenever it was lit, and to cease whenever it was extinguished. It was difficult magic, but hardly beyond her. Grandfather Black had said she could have passed her Charms OWL as a first-year, and he was hardly prone to exaggeration. Still, she tested it, lighting another candle with magic and then sharing its light with her charmed one. Sure enough, the flame began to dance and obediently fell silent when she blew it out. Satisfied, she scrawled instructions, wrapped it carefully in packaging paper and snuck downstairs to her owl.

Persephone was a slow flyer but hardly stupid, and she knew that her little gift would reach Marius sometime before morning. She pictured him opening the window to Persephone - would he be embarrassed? would he smile? - and then unwrapping it at his desk, carefully smoothing out the paper in his deliberate way, shaking his head at her illegible writing. ( _Charms are an oral art_ , she’d said to him, before he’d been sent away, when all that had passed between them was gentle teasing, not this desperate, clandestine communication.) She rather thought he would wait to light the candle until after he’d finished his work for the evening. He would ready himself for bed; he would clear his desk of all his treasures, just in case her spell went awry ( _though_ , she thought smugly, _it wouldn’t_ ). And then he would light it, and she knew what his expression would be: he would smile slowly, sheepishly, in that endearing way that he had in which one of his dimples deepened. He would remember their childhood nights, when she had charmed candles to make him laugh, and perhaps he would laugh now.

~

Her bed was cold; late summer came with its own kind of chill, and she knew it would only be stronger still when she returned to Scotland at the weekend. Beneath her pillow, tucked inside the diary that she had long since learned to carry with her, rather than hide in her room, was the woman’s name and address imprinted on beautiful, textured card. _The Viscountess Astor_ , it read. On the back, the woman - the Viscountess Astor, she supposed, whatever sort of name that was - had written her address in neat letters. _If you are ever alone in London again_ , she had said meaningfully, pressing the card into her hand as Cassiopeia climbed out of the car. She ran her fingers over the letters. Well. Perhaps it wouldn’t hurt, one day, to go pay the Viscountess Astor a visit, perhaps in the spring. She had heard whispers in Diagon Alley that London was beautiful in the spring, and she rather thought it would be.

_I have a daughter about your age,_ the woman had said, conversationally, on the drive back, and all Cassiopeia could think of, for the remainder of the trip and now, waiting for sleep, was how she wished that muggle girl was she. She supposed she didn’t feel that way when she was at Hogwarts, and perhaps that’s what made her a witch. But for now, in her bedroom, with her parents downstairs and her forgotten brother far away, she wished more than anything to trade places with that muggle girl.

 


End file.
